Towns P and Q are 120 km apart. Mr Tan drove from P to Q and was scheduled to reach Q after 2 hours. His average speed was 54 km/h for the first 40 minutes.
(a) What was his average speed for the remaining journey if he managed to arrive just on time?
(b) The time taken for his return journey is 2 hours and 10 minutes. Find his average speed for
(i) the return journey (ii) the whole trip